The invention is based on actuator technologies being developed for a wide range of applications including industry. One component used in this type of actuator is an electrically stimulated smart material actuator. These smart material actuators when electrically stimulated change shape. This shape change can be designed such that one axis predominantly changes. As this axis changes dimension it is magnified by a lever integral to the main support structure creating an actuator with a useful amount of displacement. This displacement is useful for general-purpose industrial applications such as grippers, linear motors, and consumer applications such as speakers. Presently, electromechanical devices are used such as motors, solenoids, and voice coils. In general these devices encompass many shortcomings, i.e. they are large and heavy, consume high amounts of power, and do not work in a proportional manner.
Various types of smart material actuators are known to those skilled in the art. Traditionally the smart material actuator is used two ways, first direct acting and second in a mechanically leveraged system. Most of these systems have some sort of mechanical pre-load. This pre-load has largely been used to capture the smart material actuator within the main structure. It has not generally been recognized that the pre-load force applied to the smart material actuator can affect the performance of the actuator.
In such known devices, when the smart material actuator is electrically activated, the geometry of the device expands predominantly along a predetermined axis. When the smart material device is deactivated, the geometry of the device contracts predominantly along the predetermined axis. This expansion and contraction of the smart material can be used to operate an apparatus, e.g. to open or close a gripper or vibrate a speaker cone.